function ifTest4(){
	var b = document.getElementById("btn");
	b.onclick=function(){
		var f = document.frm;
		var s1 = Number(f.su1.value);
		var s2 = Number(f.su2.value);
		var op = f.oper.value;
		var r = 0;
		if(op == '+')r = s1 + s2;
		else if(op=='-')r = s1 - s2; 	
		else if(op=='*')r = s1 * s2; 
		else if(op== '/')r= s1 / s2; 
			
		alert(r);
	}
}